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08-31-2009, 07:08 PM   #1
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Sigma 100-300 F4 question(s)...4 IMGS

Warning: Please excuse my rudimentary test with the beer bottles.

I received this lens on Friday (2nd hand) and had a chance to shoot Saturday (briefly). Unfortunately I didn't have the tripod collar (arrived today) and had to hand hold. To make a long story short, all shots at F4.0 through F7.1 were 'muddy' and out of focus. Oops. I figured we had an issue with the lens, but at F8.0 it was sharp as a tack. So I was very confused, considering the shutter speed was getting shorter at F8.0. However, I figured I would wait to test with the tripod collar before making a snap judgments.

To today - with the tripod collar on the lens and the lens on the tripod, I tried some test shots. Surprisingly focus seemed OK. Based on my hand held test Saturday (maybe it was an anomaly), I thought for sure I had an extreme back focus issue and F8.0 allowed the subject to finally come in focus. Looking at the shots today, I think it is pretty close, maybe slightly off one way or the other, but very close. Based on reviews, I was expecting F4.0 to be very sharp. See the images below.

All shot DNG, A-Priority, ISO 250, +.3 EV (always on my K200D), 300mm on the tripod with 2 second timer, mirror lock up.

The closest Corona bottle is the focus point. Nothing done to these except resize.

F4.0, 1/125




F5.6, 1/60




F8.0, 1/30




F11.0, 1/15




Another weird thing... Every shot at F4.0 seems to be underexposed by 1/3 to 2/3 EV. Not as evident in these shots, but trust me, it is always the case.

Any thoughts on the under exposure or the focus?


Thank you!


Last edited by joeyc; 08-31-2009 at 08:47 PM.
08-31-2009, 07:42 PM   #2
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QuoteOriginally posted by joeyc Quote
Warning: Please excuse my rudimentary test. I received this lens on Friday (2nd hand) and had a chance to shoot Saturday (briefly). Unfortunately I didn't have the tripod collar (arrived today) and had to hand hold. To make a long story short, all shots at F4.0 through F7.1 were 'muddy' and out of focus. Oops. I figured we had an issue with the lens, but at F8.0 it was sharp as a tack. So I was very confused, considering the shutter speed was getting shorter at F8.0. However, I figured I would wait to test with the tripod collar before making a snap judgments.

To today - with the tripod collar on the lens and the lens on the tripod, I tried some test shots. Surprisingly focus seemed OK. Based on my hand held test Saturday (maybe it was an anomaly), I thought for sure I had an extreme back focus issue and F8.0 allowed the subject to finally come in focus. Looking at the shots today, I think it is pretty close, maybe slightly off one way or the other, but very close. Based on reviews, I was expecting F4.0 to be very sharp. See the images below.

All shot DNG, A-Priority, ISO 250, +.3 EV (always on my K200D), 300mm

The closest Corona bottle is the focus point. Nothing done to these except resize.
Another weird thing... Every shot at F4.0 seems to be underexposed by 1/3 to 2/3 EV. Not as evident in these shots, but trust me, it is always the case.

Any thoughts on the under exposure or the focus?


Thank you!
resizing hides the problem

all edges are within one pixel width so I can't judge.

at this resolution it looks like the lens is working correctly

how about posting a 10% area of each frame around the focus point, including a bit of the label to judge the focus better.

also from the exif data, without tripod you are really working at the limit of the shake reduction assuming it was on.
08-31-2009, 07:51 PM   #3
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QuoteOriginally posted by Lowell Goudge Quote
resizing hides the problem

all edges are within one pixel width so I can't judge.

at this resolution it looks like the lens is working correctly

how about posting a 10% area of each frame around the focus point, including a bit of the label to judge the focus better.

also from the exif data, without tripod you are really working at the limit of the shake reduction assuming it was on.

This is true, I suppose it would be good to add that element (crops) to this exercise.

Shake reduction was off, 2 second timer with mirror lock up, on the tripod.
08-31-2009, 08:30 PM   #4
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When I got this lens, it took me half a day of testing to determine that it was front focus by 10mm and my K20D resolve it easily in the adjustment. BTW, with you handholding at 300mm , your shuttle speed is to low make the test accurate. Crank your shuttle to 1/320 F4 and test again. Many times, I found it was camera shake that caused my focus to be out and therefore soft or blurry shots. I could handheld this lens maximum at 1/60 @ 300mm but that was in a room and I am leaning against the wall. Once I am outside, I try to maintain at 1/250 if possible and if it goes lower, I will steady myself before I take a shot.

08-31-2009, 08:46 PM   #5
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QuoteOriginally posted by simdavid Quote
When I got this lens, it took me half a day of testing to determine that it was front focus by 10mm and my K20D resolve it easily in the adjustment. BTW, with you handholding at 300mm , your shuttle speed is to low make the test accurate. Crank your shuttle to 1/320 F4 and test again. Many times, I found it was camera shake that caused my focus to be out and therefore soft or blurry shots. I could handheld this lens maximum at 1/60 @ 300mm but that was in a room and I am leaning against the wall. Once I am outside, I try to maintain at 1/250 if possible and if it goes lower, I will steady myself before I take a shot.
Thanks for the reply. The images above are not hand held. My apologies if that was not clear. Before the tripod collar arrived, I did handhold some test shots (not posted). The shots above are on the tripod, therefore shutter speed is not relevant.

Unfortunately I have the K200D and lens adjustment on camera is possible.

Trying to determine front or back focus with such a long tele is not easy.
08-31-2009, 08:52 PM   #6
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I see, sorry about that part on handheld. Maybe you have a front or back focus issue then.
09-01-2009, 04:10 PM   #7
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I had copy of this lens which was shifting focus between f stops in really nasty way.
I mean, all focused and shot at f4 were OOF (strong BF), all focused and shot at f8 were tack sharp, and all focused at f9 - switched to MF - opened to and shot at f4 were tack sharp too
and I tested on two bodies (K10 and 100)

hope yours turns out right

BR
09-02-2009, 09:01 AM   #8
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It looks to me like you have a backfocus issue here. If you look at the blades of grass near the bottle, it looks to me like the grass behind the bottle is in focus at f4 & f6, and pretty sharp. It looks as if the DOF is large enough at f8 that the BF issue, though still present, is not severe enough to knock the subject out of focus. Just my $0.02.

09-02-2009, 09:40 AM   #9
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These shots you posted look pretty decent to me. With a lens of this size I would expect a very noticeable difference between handheld shots and tripod shots. I would never try to judge the quality of a large zoom with handheld shots. Shake reduction does a pretty good job much of the time but it's not perfect and handheld at 300mm takes a lot of practice even with shake reduction.
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